1. Field of the Invention
The present invention relates to magnetic resonance imaging (MRI) technology and, particularly to a method and apparatus for correcting distortion during MRI.
2. Description of the Prior Art
The influence of geometric distortion caused by non-uniform magnetic field on MRI is relatively large. Generally, the factors such as chemical shift, susceptibility difference or metal devices implanted in a body will lead to a non-uniform magnetic field.
Currently, a view angle tilting (VAT) method has been proposed for solving the geometric distortion problem during MRI images. The basic principle of the VAT method is to superimpose a compensation gradient on the axis of a slice-selection gradient at the same time when a readout gradient is applied, so that the view angle will be slightly tilted. This method can correct all the non-uniformity caused geometric distortions and density variations.
Although the implementation of the VAT method can correct the geometric distortion effectively, the final image by the VAT method will be blurred, and when such blurring is relatively severe, or in case that the requirement to the image definition is relatively high, then such MRI images cannot be used as an evidence for diagnosis.